1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device that flip-chip bonds together electrode terminals of a substrate and a semiconductor chip by solid-phase diffusion and underfills a gap between the substrate and the semiconductor chip using thermosetting resin.
2. Related Art
In recent years, when mounting a semiconductor chip on a substrate (circuit board) by flip-chip bonding during the manufacturing of a semiconductor device such as a semiconductor package, a method is used where electrode terminals such as bumps of the semiconductor chip and electrode terminals such as pads of the substrate are placed in contact and the electrode terminals are bonded together by solid-phase diffusion. As specific methods of bonding together the electrode terminals by solid-phase diffusion, when the electrode terminals of the substrate and the electrode terminals of the semiconductor chip have been placed in contact, it is possible to use an ultrasonic bonding method where ultrasonic vibration is applied to the semiconductor chip or room-temperature surface-activated bonding that applies pressure across the electrode terminals.
In Patent Document 1, a conventional method of manufacturing a semiconductor device using ultrasonic bonding is disclosed. The method of manufacturing a semiconductor device disclosed in Patent Document 1 is described below.
First, as shown in FIG. 5A, a substrate 92 on which a semiconductor chip will be mounted is placed on a stage 91. When doing so, underfill material (UF material) 93 is stuck or applied onto lead portions that are disposed on the substrate 92 and used to electrically connect the chip. Here, the temperature of the UF material 93 is kept constant at the UF material softening temperature by heating via the stage 91.
Next, as shown in FIG. 5B, a chip 95 that is disposed on a tray or the like and has gold (Au) bumps 95A attached thereto is attached by suction to a base surface of a horn 94 used to apply ultrasonic vibration, the horn 94 on which the chip 95 is held is aligned with the substrate 92 on the stage 91, and then the horn 94 is lowered onto the UF material 93. The temperature of the horn 94 (or the chip 95) at this time is set at a temperature where the UF material 93 softens but does not harden.
After this, as shown in FIG. 5C, after the chip 95 has been transferred onto the UF material 93, the UF material 93 turns into a gel due to the heat from above and below, and by carrying out ultrasonic thermocompression bonding at the hardening reaction temperature or below, the gold bumps 95A and the lead connection portions are joined. After such metal joining has been completed, heat energy is applied by a heating apparatus 96 provided outside the chip holding mechanism to the UF material 93 that forms a resin portion to produce the hardening reaction temperature of the UF material 93.
In addition, as shown in FIG. 5D, when the hardening of the UF material 93 has been completed, the horn 94 releases the chip 95 from attachment and is raised. When doing so, since the temperature of the horn 94 has been raised to close to the hardening reaction temperature of the UF material 93, the horn is cooled by a cooling apparatus 97 provided separately to the horn 94 and thereby lowered to a predetermined temperature.
By doing so, one chip 95 on which gold bumps 95A have been formed can be flip-chip mounted on lead connecting portions of a substrate 92 or the like onto which UF material 93 has been supplied in advance.
FIGS. 6A to 6D are characteristics graphs showing the temperature, load, and the like of the manufacturing members shown in FIGS. 5A to 5D. First, the UF material 93 is applied onto or stuck onto the substrate 92 placed on the stage 91 so as to cover the connection terminals (leads) for connecting the chip 95, and when doing so, as shown in FIG. 6A, the temperature of the UF material 93 rises to the softening temperature T1 of the UF material. After the softening temperature T1 of the UF material has been reached, the temperature becomes substantially constant. When the UF material 93 turns into a gel and the temperature of the UF material 93 is raised by the external heating apparatus 96 to reach the hardening temperature T2, the UF material 93 hardens. After the UF material 93 has hardened, since the horn 94 is cooled by the cooling apparatus 97, the temperature of the UF material 93 falls to the initial temperature.
On the other hand, as shown in FIG. 6B, the chip 95 that has been connected and fixed to the substrate 92 is attached by suction to the horn 94 on the rear surface side of the chip 95, and like the horn 94 is kept at a substantially uniform temperature T1′. This temperature T1′ is kept constant during the application of ultrasound (US) so that the amplitude of the ultrasonic vibration of the horn is kept constant. When the horn temperature is raised to T2′ by the external heating apparatus 96, the UF material 93 reaches the hardening temperature T2. After the UF material 93 has hardened, the temperature of the horn 94 is again kept uniform at the temperature T1′.
Also, as shown in FIG. 6C, the load applied to the chip when the chip is connected to the substrate is set so as to obtain characteristics that enable the ultrasonic energy to be efficiently transmitted.
As shown in FIG. 6D, the timing for producing the ultrasonic vibration applied to the horn 94 is set at the point where the applied load reaches an optimal load for connecting the gold bumps and the leads.
Patent Document 1
Japanese Laid-Open Patent Publication No. 2004-356419 (Paragraphs 0016 to 0020, 0031 to 0034, and FIGS. 1 and 4)